package com.gxzy.config;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

/**
 * 针对@ResponseBody注解的前端返回值过滤配置
 */

@Configuration
public class NullValueFilteringCfg {

    @Bean
    @Primary
    @ConditionalOnMissingBean(ObjectMapper.class)
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();

        /**
         * 通过该方法对mapper对象进行设置，所有序列化的对象都将按改规则进行系列化
         * Include.Include.ALWAYS 默认
         * Include.NON_DEFAULT 属性为默认值不序列化
         * Include.NON_EMPTY 属性为 空（""） 或者为 NULL 都不序列化，则返回的json是没有这个字段的。这样对移动端会更省流量
         * Include.NON_NULL 属性为NULL 不序列化,就是为null的字段不参加序列化
         */
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);

        /**
         * 字段保留，将null值转为""
         */
        // objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
        //     @Override
        //     public void serialize(Object o, JsonGenerator jsonGenerator,SerializerProvider serializerProvider)
        //             throws IOException, JsonProcessingException {
        //         jsonGenerator.writeString("");
        //     }
        // });

        return objectMapper;
    }
}